I'm working through a passage and I have to identify verbs, their forms and their subject and object.

I'm having trouble with a side comment: "neque erat difficile scire" (and it was not difficult to know)

I know that my main verb is erat and the object is the predicate adjective difficile. So that suggests to me that "erat" is a copulative (linking) verb with an internal subject. Or is this an impersonal verb? Or is there another term for this kind of construction.

I agree. We are all at different levels of understanding or learning, and what may seem simple to one person may appear very complex to another. There is no utility in a dismissive type of response. It limits discussion and sets up barriers for asking questions, to the detriment of us all.